Explanation:
Few star clusters are seen to be so close to each other.
Some 7,000 light-years away, though, this pair of open or galactic
star clusters is an easy
binocular target, a lovely starfield in the
northern constellation
Perseus.
Also visible to
the unaided eye from dark sky areas,
it was cataloged in 130 BC by Greek astronomer Hipparchus.
Now known as
h and
chi Persei, or
NGC 869 (above right) and NGC 884, the clusters themselves are separated by only a few hundred light-years and contain stars much younger and hotter than the Sun.
In addition to being physically close together,
the clusters' ages
based on
their individual stars are similar - evidence that both
clusters were likely a product of the same
star-forming region.